The present invention relates in general to an apparatus for generating broadcast signals. More particularly, the present invention relates to an apparatus for converting broadcast signals compatible with a first broadcast system into broadcast signals compatible with a second broadcast system.
Generally, to receive or send broadcaste signals between areas which adopt different TV broadcast systems, the broadcast signals must be converted into formats that are compatible with the respective TV broadcast system. Presently, the various TV broadcast systems, such as NTSC, PAL, and SECAM broadcast systems, are different from each other. Therefore, to transmit a TV broadcast signal from an area which employs a PAL TV broadcast to an area which employs an NTSC TV broadcast, as an example, the TV broadcast signal of the PAL system must be converted into a format compatible with the TV broadcast signal of the NTSC system.
The respective broadcast systems have different specifications for sync signals as well as video signals. Thus, when the broadcast signal is converted, the sync signal must also be converted so that it is consistent with the broadcast system of the converted TV broadcast signal. The sync signal of the TV broadcast signal is a composite sync signal which is produced by combining a horizontal sync signal, a vertical sync signal, an equalizing pulse, etc. The components constituting such a composite sync signal have different specifications for the different broadcast systems. Therefore, to convert the sync signal, the aforesaid components of the sync signals must all be converted and then combined to form a composite sync signal that is consistent with the receiving broadcast system.
However, in conventional sync signal generating apparatus, the number of the convertible broadcast systems is limited to a single type of broadcast system. Accordingly, only limited conversion is possible. Moreover, because the odd and even fields of the sync signal are not distinguished from one another, the converted sync signal will include errors.